I've had Mathilda since early 2013. She, Gruff, Cyrano, Queenie and Astrid have been in my town for 2 and a half years now. But she was the first of the 5 to move in. As for the rest they're fairly new to my town.
I've had Punchy and Genji since day one in my town, August 23 of last year. I was lucky to get a bunch of villagers I liked right from the start, but the others have long moved out.
The next longest I've had other than Punchy and Genji is Willow, and I got her May 30th > V <
Walker, Fauna, and Tangy. My original trio ever since starting the game last July. I've cycled through a handful of villagers from that point up until now and those three are just stuck with me forever...whether they like it or not. (oops)
Alice has been in my town for over a year. She is my last original/starter villager. I started playing on Sept. 22nd, 2014, and now it's Oct. 6th, 2015, so....yeah.
Tangy moved from my main town to the new one I created, and I love her I'm pretty sure Roscoe has been in my current town the longest but its only been a few months... I change mine a lot
Lolly She's is currently my last villager I've had since I've started playing on December 26th, 2013. I wasn't into her at first, but I suddenly started loving her once I got used to her. As much as I love her and she's my last original villager, I do wanna give her away after I get rid of three of my unwanted villagers.
Out of all of my villagers, including the one's I've had in previous games, I've probably had Poppy the longest. I had her since my early days of playing New Leaf, which was two years ago, and I never want to let her leave :3
I also had Alfonso and Felicity as starters in my first CF town and had them for a year or two, until they either moved away or my first Wii broke (I can't remember).
I've also probably had Stitches for a long time. He's lived in my first WW town for a while, and he's lived in my NL town for some time, though I can't remember how long exactly. He's moved out of my town, though.
I've had all of my villagers except for Punchy and Tangy for over a year. I think Ankha, Kabuki and Moe have lived there the longest at least two years though.
ankha was a starting villager in my town. so a year and 10 months ^^ stitches and jacques were random moves in shortly after, but i lost them due to reckless TTing, but i cycled 16 villagers to get them back and i've had them ever since
Started on the release date and all 10 are still living in my main town. All were villagers that the game gave me and I love them.
In my guest town I have none of them because it was a TT town and lost them all. Right now I have a nice group of villagers but might let Peggy go. I like the placement of her house and can't do plot resetting.